This invention relates generally to equipment for processing semiconductors, and more particularly to methods and apparatus for rapidly cooling substrates.
There are numerous semiconductor process steps involved in the development of modem day integrated circuits (ICs). From the initial fabrication of silicon substrates to final packaging and testing, integrated circuit manufacturing involves many fabrication steps, including photolithography, doping, etching and thin film deposition. For many of these processes, temperature is a key factor for obtaining desired film properties and characteristics. Characteristics of thin film metals and dielectrics affect electronic properties such as resistive and capacitive values, thus directly affecting IC performance characteristics such as device speed and power consumption.
In most semiconductor processes, heating by radiation is the preferred mode for heating because of its rapid heating capability compared to heating by conduction and convection. In a system where single wafers, or wafer batches are being processed, wafer throughput would be directly affected by the rate at which each wafer or each batch of wafers are heated and subsequently cooled. In such systems where heating by radiation is employed, a rapid cooling method should compensate to otherwise not compromise the high wafer throughput achieved by the rapid heating by radiation process.
These and other needs are satisfied by several aspects of the present invention.
In accordance with one aspect of the invention, a workpiece is placed on a support or susceptor within a process chamber, and processed to an elevated temperature. A radiation-absorbing medium or material element is positioned between a reflective surface and the workpiece after a semiconductor process. The material element is spaced from the workpiece more than about 5 mm. The medium allows for the processed workpiece to cool from the elevated temperature.
In accordance with another aspect of the invention, a method is provided for processing a substrate in a semiconductor-processing chamber. A semiconductor substrate is placed on a substrate support within the processing chamber. A radiation-absorbing material element is positioned between a reflective surface and the substrate after heating of the wafer, outside the processing chamber.
In accordance with another aspect of the invention, a high temperature processing apparatus is provided, including a processing chamber and support the chamber for supporting a substrate. A plurality of heat sources are positioned outside the processing chamber to provide radiant energy to the substrate. A highly reflective surface placed outside the heat sources promotes an efficient conveyance of radiated energy to the substrate. A movable radiation-absorbing material element is included. The apparatus is configured to move the movable element from a process position that does not interfere with heating the substrate during a fabrication process to a post-process position between the reflective surface and the substrate after the fabrication process.
Advantageously, the preferred method provides significant time savings over previous methods by expediting the cooling process of a wafer after a semiconductor process is completed. The introduction of a radiation-absorbing material element between the reflective surfaces and the wafer inhibits radiation from returning to the wafer, which would generally slow the cooling rate of the processed wafer. Conversely, rapid cooling of processed wafers thus improves overall wafer throughput.